Calculate the Luminosity Contrast Ratio of two colors to determine whether text can be easily read. This quantifies the legibility of colored text on a colored background for accessibility purposes.
Implements the formula in WCAG 2.0 guideline 1.4
A recommended value is at least 4.5:1 (4.5) for standard text, or at least 3:1 (3.0) for large text.
Add this line to your application's Gemfile:
gem 'luminosity_contrast'And then execute:
$ bundle
Or install it yourself as:
$ gem install luminosity_contrast
LuminosityContrast.ratio('000', 'fff')
# => 21.0
LuminosityContrast.ratio([0,0,0], [255,255,255])
# => 21.0
sienna = LuminosityContrast::Color.new('A0522D')
LuminosityContrast.ratio(sienna, sienna)
# => 1.0
midnight_blue = LuminosityContrast::Color.new('191970')
sky_blue = LuminosityContrast::Color.new('87CEEB')
midnight_blue.ratio(sky_blue)
# => 8.5256628387305
sky_blue.ratio(midnight_blue)
# => 8.5256628387305After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.
To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.
Bug reports and pull requests are welcome on GitHub at https://github.com/devpuppy/luminosity_contrast. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.
The gem is available as open source under the terms of the MIT License.